Top fuel saving myths: How to keep fuel costs down

We sort the fact from the fiction

23rdSep2015

There's no denying that the cost of running a car can add up. As petrol prices go up and down it's often a race to see what will come first, a price drop or an empty petrol tank..

It's even more noticeable in winter, when your miles per gallon performance is worsened by the harsh weather. It's no wonder then that we all keep an eye out for the latest fuel saving tips. Whether it's a new way to drive or a mystical new piece of kit, we'll try it all to get the most out of our tanks.

But be warned - not all tips you might come across work. Some tips even have a detrimental effect on your fuel consumption! So sort the myths from the trusted tips by checking out our top 8 below:

1. A smaller car equals a smaller fuel bill

There is a myth that the best way to save money on fuel is to simply downsize your car. This may have been the case in days gone by, but with modern motors the difference between the fuel consumption of large and small cars has reduced considerably. New technologies such as stop/start and advanced automatic transmissions have helped to bridge the gap.

Just look at the new Jaguar XE - breakthroughs in aerodynamics, lightweight construction and new engines means this mid-sized saloon can achieve 71.7mpg. Hybrid systems, which are also extremely economical, now tend to be fitted to vehicles of every shape and size.

2. It's better to leave your car idle than turn the engine off

You often hear the myth that if you're sat in traffic or held up at the lights, that it's best to keep your engine running. However, that's not always true. Modern fuel injection systems are more efficient than you might think, and use very little fuel to start an engine (especially one already warm from running) meaning it might save you more gas to turn your engine off when stationary.

Of course, if you're in constantly moving queues it's best to keep the engine on, or you could risk wearing out your starter motor.

3. Filling up when it's cooler outside will get you more fuel

Based on the science that liquid is more dense when at a lower temperature, it's been purported that choosing to fill up when it's cold outside will get you more for your money. A good theory in principle - but considering that petrol is contained in huge underground storage tanks, this myth doesn't really hold up. Stored underground, outside temperature differences have little or no effect on fuel. Good news for us all really, as fuel is naturally cooled to give us the most possible all year round.

4. It's best to warm your engine up before setting off

It's true that a warm engine is more fuel efficient, and that cold starts in the morning probably use more fuel then at any other time. But after you've started the engine, the best way to warm it up is to drive it. The myth that leaving your engine on for a couple of minutes to warm up will make your journey more fuel efficient simply isn't true - and in fact you'll probably end up using more fuel running it idle.

Of course in winter, you need to ensure that your windows are clear - but the best way to clear these is with de-icer and a scraper. Turn your engine on just as you're about to set off.

5. Shifting in to neutral when stationary saves fuel

It used to be the case that shifting in to neutral at idle would save on fuel, as many engines featured carburettors instead of fuel injection. However thanks to computer-controlled fuel injection systems, fuel flow shuts off when the engine is revving above idle, meaning that an equal amount of fuel is used whether sat in gear on in neutral.

In fact, if you're travelling downhill, you will use more fuel shifting in to neutral than staying in gear. Most modern engines use no fuel at all if left to descend a gradient in-gear.

6. Less fuel in the tank equals more mileage

It's completely true that heavier loads in your car will use up more gas. That's why many of us choose to fill up only between a quarter and a half of our tank to keep our cars lighter. The principle in this theory is a sound one - and it probably does save some fuel. However, the amount saved is probably so small that it's not actually worth doing. Factor in the added trips to the petrol station that this causes - and it probably costs you more than it saves.

7. Wind your windows down instead of using air conditioning

Much like the chicken or the egg, it's the age-old question of air conditioning against open windows. Which one saves you more fuel? The truth is that air conditioning does use up fuel, but not as much as you'd think. At higher speeds, using air conditioning is much more cost effective than winding your windows down, due to the drag created by opening a window ruining the aerodynamics of your car.

However at lower speeds, for example in suburban areas, an open window is a viable alternative which lets you turn of the air conditioning and lower your fuel consumption. The honest answer is that both methods have a time and a place.

So there you have it! Some to fuel saving tips - to avoid. So we've busted some myths, but what methods are actually proven to keep gas bills down?

1. Stay light-footed on the gas

It seems obvious, but the further your foot is down on the accelerator, the more fuel is injected in to the engine. The best method is to stay in lower gears when accelerating, and then switching in to a higher gear at the desired speed. This means you can avoid having your foot to the floor wherever possible. As a general rule, being gentle with the accelerator is one of the biggest factors in improving fuel efficiency.

2. Check your tyre pressures

It's something which many of us can forget about unless setting off on particularly long journeys - but it can be really beneficial to check your tyre pressures all year round. Aside from making sure you stay safe on the roads by identifying any slow punctures, checking that the tyre pressures are correct can really help your fuel economy.

If your tyre is under-inflated this causes it to drag, not only reducing your fuel economy but also increasing wear on your tyres. Many petrol stations offer a free air pump for you to adjust tyre pressures to the correct level.

3. Plan out your route beforehand

This may seem an odd choice at first, but how many times have you set off on an unfamiliar journey and hit a thick wall of traffic? Being stuck in traffic is one of the biggest gas-guzzling culprits out there, especially when it's slow moving and there's no chance to turn off the engine.

Your best bet is to plan your route before you set off. You may decide on a longer route to avoid road works or accidents, but ultimately the overall journey time will be shorter and the consistent speed will keep you away from the petrol stations for longer.